Preparation of pigmented coatings



Patented Aug. 20, 1940" PATENT OFFICE 2,211,912 I ranrm'rronor PIGMENTED commas Patrick J. Ryan, Royal Oak, Mich., assignor, by -mesne assignments, to Reichhold Chemicals, Inc., Detroit, Mich, a corporation of Delaware No Drawing. Application May 9, 1938,

Serial No. 206,923

1 claim. (on. 2611-40) The invention relates to improved pigmented coatings and to the method of preparing the same.

The conventional method for preparation of 5 pigmented coatings consists in wetting and dispersing a pigment in an organic solvent solution of a film forming matelial, such as mixtures of drying oils and synthetic resins.

Among the objects of my. invention are to obtain better wetting and dispersion of pigments, higher original gloss, superior gloss retention, better original color and better color retention, than is obtainable by conventional methods now in use. Another object is to shorten the time requiredffor'processing.

It is known that good gloss in coatings dependsalmost exclusively upon proper wetting and dispersion of pigments. This gloss is' obtained by present methods by long-grinding and mixing in pebble mills .or, by repeated passes through a. roller mill or stone mill. The purpose of this long grinding time is to obtain satisfac tory wetting and dispersion of the pigment agglomerates by 'mechanical means. The word "grinding is used throughout the industries to designate wetting and dispersion of pigments in various vehicles and that word has been retained in this application to designate such and not to indicate a reduction of particle size of the pig- 0 ments used. Pebble mills are considered to have advantages-over roller mills and stone mills insoiar as no volatile losses are incurred during the processing, but it usually requires long periods of processing in a pebble mill before satis-" factory gloss is obtained. Hence, many in the industries have abandoned it in favor of the roller mill or stone mill. j x

My invention comprises pre lvetting and at least partially dispersing pigments irrsfiitable oro ganic solvents for the film forming agent to be subsequently added and then introducingfilm forming substances into said mixture and applying sufflcient, mechanical forces to complete the dispersion. The employment of my invention 5 has decreased the grinding time of pigmented coatings from one-half to two-thirds the time normally used when processed by conventional method. v

The process may be carried out without necessarily employing super atmospheric pressure,

vacuum or increased temperature, though it will be understood that any ,of these factorsmay be present if desired, .or if necessary in specific cases. The process may also be carried out with-. out the loss of the volatiles used. 5 The invention will be more readily understood by reference to the following specific examples which are set forth by way of illustration and not by way of limitation:

The above was charged into a pebble mill and tumbled for 10-15 minutesand the following was added:

' Parts by weight 30 Vehicle (A) 450.

The mm was then tumbled for '12 hours and the following added: p r

. Parts by weight Vehicle (A) i150 'jHigh solvency petroleum naphtha I 302 The enamel prepared in this way was compared to one prepared by the following conventional method:

- Parts by weight Titanium dioxide 950 Zinc oxide- 50 85 High solvency petroleum naphtha 270 Vehicle (A) The above was charged into the pebble mill in one operation and tumbled for '72 hours and the 40 following was added: a

' Parts by weight Vehicle (A) 1150 inch solvency petroleum naphtha 302 etc! phthalate soya bean fatty acid modified resin, dissolved in equal parts by weight 01' xylol.

Erample II Partsbyweiaht Titanium dioxide 1425 Zinc oxide High solvency petroleum naphtha 420 The above was tumbled for 10-15 mlnutes in a pebble mill and the following was added:

Parts by weight Vehicle (A) Y 630 The above was tumbled for the hours shown in Table I, and the following was added at the end oi! the time shown in the table:

Parts by weight Vehicle (A) 1010 High solvency petroleum naphtha 350 The coatings prepared in the above manner were compared to coatings prepared as follows:

Parts by weight Titanium dioxide 1425 Zinc oxide 75 High solvency petroleum naphtha 420 Vehicle (A) 630 The above was tumbled for the hours shown in Table I, and the following was added at the end,

of the time shown in the table:

Parts byweight Vehicle (A) 1010 High solvency petroleum naphtha 350 Table I Tumbled out! hours Erample I] New way issssess sesaass Example 11 Old wayn 0. Used as standard. Equal.

It is to be noted that the pigments, solvents and vehicle were all from the same source. The films were applied in the same manner, and baked at the same schedule, theonly diiference being in the preparation of the coatings as dewith a further quantity of the volatile petroleum hydrocarbon.

PATRICK J. .RYAN. 

